I read this for the Cape Fear River Watch book club.
This is a book by a prominent freshwater fisheries biologist. It’s a combination memoir and nature book with a large dose of advocacy. The author had a long career studying streams throughout the world, including in Japan and the western US. There is a lot of science in it, trying to untangle the ecology of streams and their place in the surrounding woods. It turns out that streams and the fish that live in them are closely connected to the forest nearby via the transport of insects across the surface and algae living on the rocks. The author’s technique of enclosing streams with nets is unusual and very involved. If you change the ability of insects to fall into a stream, or get out of a stream and fly into the forest, you will change the nature of the forest substantially.
The author spends a lot of the book talking about how different species of fish living in the same part of a stream interact. Usually it seems, one species comes to dominate over the others and drive them out, especially if the dominant species is invasive. It’s sad to see gorgeous fish such as Dolly Varden Charr or Cutthroat Trout being forced out of their native territory by invasive or hatchery-raised fish like rainbow trout. From reading this book, it does not look like there is much that humans can do to stop or reverse this process. In addition, native fish are threatened to channelization, dam building and development. The populations of these native fishes will continue to decline over the years as they get forced further and further up watersheds and become genetically isolated. The forests and streams have evolved to support and depend on the native fish. Who knows how this will all play out.